The invention relates to a microscope for transmitted-light, reflected-light or combined transmitted-/reflected-light illumination for the investigation of large-surface-area objects, such as masks or wafers.
As optical instruments which serve, for example, for the inspection or the measurement of wafers or the alignment of mask and wafer, semiconductor microscopes and special-purpose mask comparison microscopes (double microscopes) are known which, in conventional fashion, possess one (or more) optical axis (axes) in the vertical position and one (or more) object stage(s) in the horizontal position.
The highly sensitive precision objects (wafers) with their currently known dimensions (up to 150 mm diameter) can admittedly be inspected or measured in an efficient manner using these known microscopic examination instruments. However, the wafer generation of the future will, inter alia, be characterized by an enlargement of the wafer diameter to 10 inches and more, and also by an increase in the object-specific structure density.
The following disadvantages and risks during wafer handling and investigation using the known types of semiconductor microscope arise from this:
the position of the large-surface-area wafer on the horizontal object stage leads to a greatly increased danger of breakage or scratching, particularly in its peripheral regions;
the operational possibilities are obstructed for the observer in an anti-ergonomic fashion;
the necessarily increased range of movement of the mechanical object stage in the horizontal x-y plane is limited or restricted by the microexamination position of the observer and by the instrument design;
the danger of contamination of the wafer surface increases in a dramatic and uncontrollable fashion, which becomes evident, for example, merely from the fact that even the very smallest dust particles, which can only be detected by microscopy, emanating from the body or from the clothing of the person impair the functions of a highly integrated circuit;
the area space requirement of a known semiconductor microscope to be equipped for such objects or of an entire inspection station to be equipped for such objects increases correspondingly;
stability problems caused by the design arise for the microscope.